...there is no cgmanager in Bionic / Mint 19.
Theoritically, you could try sudo systemctl disable cgmanager (or mask instead of disable)...or purge cgmanager altogether.
Since it's an upgrade though & not a clean install, i'd start by trying to disable such first.

aakerbeere, pretty much anything related to cgmanager is obsolete under Mint 19...
(ie. the reason i said to take note of dependencies is because when doing an upgrade instead of a 'clean' install,
it's certainly not unheard of ending up with newer packages half-installed and/or older ones not removed...)